Apparatus for electrolyzing salt solutions



T. MATSUSHIMA.

APPARATUS FOR ELEGTROLYZING SALT SOLUT| 0NS.

APPLICATION FILED MAR. 18, 1918.

Patented Feb. 15, 1921,

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APPARATUS FOEELECTRQLYZINGSAIT SOLUTIONS.

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Specification of Letters Eatent. Patentgfl Feb, 15 921 Application filed March 15, 1918. Serial No. 223,180.

I To all whom it may concern Be it known that ll, TADAO MATSUSHIMA, a subject of the Emperor of Japan, residing at No. 599 Midoricho Shichome, Ashigaragun, Kanagawaken, Japan, have invented certain new and useful Improvements in Apparatus for Electrolyzing Salt Solutions, of which the following is a specification.

This inventidn relates to an apparatus for electrolyzing salt solution by a mercury process, in which the inner surface of a porous bottom of an inner tank is covered by a thin layer of mercury short circuited to cathode pole introduced therein, and this tank is arranged within an outer tank having an anode pole. inner tank is spaced away from the bottom of the outer tank, so that caustic soda solution in the inner tank and salt solution in the outer tank are perfectly separated I from each other by means of the said layer of mercury, whereby sodium amalgam is produced on the lower surface of the mercury layer, which, passing through the v layer, comes to the upper surface thereof and is decomposed to produce caustic soda therein. 'The object of the invention is to greatly decrease the quantity of mercury required, to avoid the necessit of circulating the amalgam and accordingly to save the power for its circulation, thus eliminating the loss of mercury, which necessarily arises in the circulation of mercury in the known method,' by preventing its oxidation;' in short, toproduce a pure and concentrated product with far better efficiency of working current.

An accompanying drawing shows'a s ec tional elevation of an apparatus according The bottom of the loss of such mercury cannot be avoided during the said circulation.

According to this invention, these dra-wbacks are all eliminated. For this purpose an apparatus according to this invention comprises, as shown, an outer and an inner tank. The latter is provided with a cathode and the former with an anode. tom of the inner tank consists of porous material which can support-mercury and the upper'surface of the bottom is covered with a thin horizontal layer of mercury, which in this inyention is short circuited to the cathode. The inner tank is also suitably provided with supply for salt-solution, deliveries for salt solution, caustic soda solution and for gases. Current passes from anode, through salt solution to the lower surface of the bottom of the inner tank, the upper surface thereof, mercury layer and then the majority of it through caustic soda solution to cathode, and partly through short circuit directly to cathode. This layer of mercury separates both solutions horizontally and the amalgamation is produced on the lower surface thereof while the recovery of the mercury is completed on the upper surface. Therefore the mercury according to this invention performs a simultaneous 'double action, so that no additional mercury is required. In the apto this invention in whichTA is an outer eparatus used heretofore a certain quantity tank, B an inner tank, C the porous bottom of the inner tank, D an anode pole, E a mercury la er, F a cathode pole, G salt solution, H caustic soda solution, 1 water iniet, J delivery for caustic sodas solution, K delivery for hydrogen gas, L delivery for chlorln gas. Inlet and outlet for salt solution are omitted in the draw-' 'to improvements in an apparatus for the electrolysis of salt solution according to the. well-known mercury process, which is rec-" ommended, among hitherto known processes for producing caustic soda, chlorin of mercury is required in the recovering chamber in addition to the quantityof mercury required in the amalgamation chamber. Therefore even, considering only this point, the quantity 9f mercury re uired in this apparatusis decreased by hal as compared with the known ones. Moreover, in the known apparatus for the mercury procr ess,'because amalgam Iproduced on the up-v The invention more specifically relates] 0 per surface of the me ury has less specific grau'ty than the mercury itself, said amal-,

.centage of sodium ,contentin the amalgam,

the apparatus known heretofore has a great The bot- The porosity of the bottom of the inner tank drawback. 1h contradistinction to this, in the present apparatus, the amalgam produced on the lower surface of the mercury layer immediately passes through the mercury and comes upon the upper surface thereof. Therefore there is no hindrance in the amalgamation even with a high percentage of sodium content.

The fact that the required quantity of mercury is small in this apparatus, is based upon not only the double action of the surfaces of the mercury, but also upon the saving of part of the mercury which otherwise fiows through the transmitting mercury circulation tubes or pumps.- The reason for this, is that mercury in this invention canbe recovered from amalgam in one and the same POSItIOII. Moreover, because mercury does not flow and the amalgam produced on the lower surface thereof floats to the upper surface and is recovered at once, the

thickness of the layer can be greatly reduced.

' port the mercury, and the separation of the two liquids is made by the mercury itself. Therefore, the separation of the two liquids is perfectly achieved the same as in the other mercury process and a pure and concentrated product can be equally obtained.

permits, the passage of the amalgam therethrough. 'The purpose of short circuiting t e cathode and mercury layer in the inner tank is to prevent; oxidation of mercury which may occur when amalgam to be decomposed is insufiicient as compared with the quantity of current passing through the inner tank. An amplespaceis provided between the bottoms of the two tanks. for increasing the .sectional area of electrolyte in order to decrease its eledtric resistance.

The working of this apparatus'is as follows. The outer tank is filled with saturated salt solution and the inner tank with dilute caustic soda solution, a circuit being thus closed between the tanks, twd electrodes and a source of direct current. Chlorin gas generated in the anode can not dissolve in the concentrated salt solution, and it is therefore permitted to escape from the gas outlet. Sodium produced on the lower surtrated, it is taken out of its outlet and water is supplied, the salt solution being always maintained in concentrated state. Care must be taken during the working to maintain the level of the caustic soda solution always higher than that of water. @ne can thus prevent salt solution from flowing into the inner tank.

I claim:

1. An apparatus for electrolyzing salt solutions, comprising an outer tank having an unobstructed lower portion and containing a salt solution, an anode pole extending into said salt solution, an inner tank located in the first tank and containing a caustic soda solution, a porous imperforate bottom carried by the inner tankand spaced away from the bottom ofthe outer tank, a thin .horizontal layer of mercury supported by the porousbottom, and a cathode pole extending into said caustic soda and in ,electrical engagement with said mercury layer.

2. ,An apparatus as defined in claim 1, in which the first tank isg provided with a chlorin gas outlet.

3. An apparatus as defined in claim 1, in which the inner tank is provided with outlets for-caustic soda solution and hydrogen gas, and an inlet for water.

When the In testimony whereof I have hereuntov set T my hand in presence of two subscribing witnesses.

TADAO MATSUSHIMA.

Witnesses:

GENJI KURI ARA, Hrsnsm BEPPU'. 

